Durability Performance of Waste Rubber Fiber-Reinforced Geopolymer Concrete Using the Taguchi Method

Abstract This study investigates the durability performance of waste rubber fiber (RF)-reinforced geopolymer concrete (RGPC) by evaluating the effects of rubber fiber content, ground granulated blast furnace slag (GGBS) percentage, and curing temperature (CT) using an L 9 ( 3 3 ) Taguchi design. The influence of RF (0.6%, 0.9%, 1.2%), GGBS [25% GGBS–75% fly ash (FA), 50% GGBS–50% FA, and 75% GGBS–25% FA], and CT (75°C, 90°C, 105°C) on water absorption (WA), sorptivity, water permeability, magnesium sulfate ( MgSO 4 ) resistance, and drying shrinkage was examined. Microstructural characteristics were assessed through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses, and the statistical significance of each parameter was determined using ANOVA. Increasing the GGBS percentage markedly improved transport-related durability: water absorption decreased from 5.62% at 25% GGBS to 2.31% at 75% GGBS (a 58.9% reduction), and the initial sorptivity coefficient decreased fourfold. Water penetration depth also decreased from 50 to 22.7 mm with higher GGBS content. RF incorporation increased water absorption and sorptivity but enhanced MgSO 4 resistance; mixes with high FA content exhibited ultrasonic velocity increases of up to 9.86% after 12 weeks of MgSO 4 exposure. Increasing the CT from 75°C to 105°C reduced drying shrinkage from 0.052% to 0.023%, representing nearly a 50% improvement. SEM–EDX results confirmed that higher GGBS levels produced denser C─(N)─A─S─H gel structures, consistent with improved durability. Overall performance optimization identified the A1B3C3 mix (0.6% RF, 75% GGBS, 105°C CT) as the optimum combination. Among all parameters, GGBS proved to be the dominant factor influencing RGPC durability.